Fabrication of hollow SiO2 and Au (core)–SiO2 (shell) nanostructures of different shapes by CdS template dissolution

Abstract

Core–shell silica (SiO2) coated CdS nanorods (NR) and nanospheres (NS) were prepared (SiO2@CdS) by deposition of a Si–O–Si amorphous layer over the CdS surface through the hydrolysis of 3-mercaptopropyltrimethoxysilane and tetraethylorthosilicate. Nanoporous SiO2 matrix (NPSM), hollow SiO2 nanotubes (HSNT) and nanospheres (HSNS) useful for efficient adsorption and catalytic processes were prepared by chemical dissolution of CdS–NS (size: 9–10 nm) and CdS–NR (length: 116–128 nm and width: 6–11 nm) template from SiO2@CdS with 2 M HNO3. These SiO2 nanostructures were characterized by optical absorption, TEM, EDX, SAED and BET surface area analysis. TEM images revealed the fabrication of slightly distorted HSNS (size: 9–12 nm) and closed HSNT (length: 30–45 nm and diameter: 9–14 nm) of shorter dimensions than the CdS–NR template used. The BET surface area (112–134 m2 g−1) of NPSM and HSNS is found to be larger than the surface area (29–51 m2 g−1) of SiO2@CdS composites indicating hollow SiO2 morphology. Silica coated Au (SiO2@Au) composites formed by CdS dissolution from Au (2 wt%) deposited CdS–NR core-encapsulated into SiO2 shell (SiO2@Au–CdS–NR) exhibited a surface plasmon band at 550 nm and displayed high catalytic activity for 4-nitrophenol reduction by Au nanoparticle.